Revise the topics. You should have started with some easier ones in year 7, so there’s shouldn’t really be a need to revise those, but rather review them. Read your notes, or textbooks, and pick out the things that you don’t particularly know or remember. Basically try to revise the things that you find difficult, rather than everything you wrote in your books ( just a waste of time in my opinion, with all the extra tasks the teachers set that are there mostly for short term recall). With maths specifically just do topic exam questions, and for all subjects just look at the specification from your exam board.